That angle aluminum is perfect- one suggestion: Maybe if you have clearance, I would put the "down" side of the alum on the "inside" wall of the stringer, so the top (flat side that the floor will rest on) also sits on the top of the stringer... still facing the same way you have it in the drawing, just on the opposite side of that stringer. That way your not relying only on bolts to hold it in place. Hope that makes sense...Great CAD drawings by the way...
Entire floor was grinded and sanded then covered in one layer of 1708 except in the rear where there was a lot of oil canning so I used 2 layers of 1708 and one layer of 24 oz roving.